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    <title>Document</title>
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<body>
    <script>
        const promise1 = new Promise((resolve,reject) => {
            console.log('promise1')
            resolve('resolve')  // 立刻 第一个宏任务  pending -> fullfilled
        })
        // promise.then 的返回值还是promise
        const promise2 =  promise1.then(res => {
            console.log('res')
             return new Promise((resolve,reject) => {
                resolve()
                console.log(promise2,'-----')
            })
        })
        console.log(promise2,'----')
        console.log(1,promise1); // 1 Promise{pfullfilled}
        console.log(2,promise2)    // promise {pending}
        
    </script>
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